Rutile and anatase TiO2 nano particles with Ni doping were synthesized by mechanical alloying, and were characterized by XRD, TEM, UV-DRS and photoluminescence (PL) spectra. The relationships between crystal type and photocatalytic activity as well as the mechanisms of transition metal doping on TiO2 lattice were studied. The results showed that the rutile type TiO2 with Ni led to higher photocatalytic activities.